A Guide to Electroless Nickel Plating Services at Micro Plating

Micro Plating - Experienced Uniform Nickel Plating

Electroless nickel plating services (ENP) are a revolutionary metal finishing process first developed in the mid-20th century for the uniform deposit of nickel without requiring an external electrical current. Micro Plating Inc., in Erie, PA, has solidified itself as one of the region’s premier providers of electroless nickel plating services with a focus on providing uniform RoHS-compliant solutions that meet varying ASTM, ASM, and Mil-spec requirements. This position at the forefront of the industry was not accidental and is a culmination of Micro Plating’s dedication, experience, and continual technological advancement.  Electroless nickel plating services do not require a costly influx of electrical current and instead is an auto-catalytic reaction that relies upon a series of chemical treatment baths and rinses to develop the hardened and corrosion-resistant exterior highly valued by modern manufacturers and fabricators. This results in faster turnaround times, reduced costs, and enhanced uniformity and quality. 

This article will provide a more detailed definition of ENP, the ways to properly prepare materials, more information on the plating technique, the plating bath, how ENP varies from anodizing or hard chrome, the many applications, as well as the advantages and disadvantages of electroless nickel plating services.

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Electroless Nickel Plating - A History

The discovery of electroless nickel plating is officially credited to Abner Brenner and Grace Riddell, who developed the process in the mid-1900s. Since its inception, electroless nickel quickly became a commercially integral process for finishing steel, aluminum, copper, plastics, and other materials as it was a less expensive solution that did not require costly and sometimes hazardous electrical current. To develop ENP, the researchers introduced varying reducing agents to an operational electroplating bath in the hopes of preventing the detrimental oxidation reactions taking place at the anode. 

Eventually, they discovered one reducing agent increased the amount of deposited nickel at the cathode end of the reaction. Sodium hypophosphite appeared to surpass the theoretical limitations of Faraday’s Law which states that the mass of a deposited substance at an electrode is directly proportional to electrical charge. A year after this discovery, Brenner and Riddel presented their findings at the American Electroplaters Society Convention and subsequently proposed the new “electroless” alternative as well as the carefully calculated bath compositions that created the eventual patented process. Since this time, electroless nickel has been further optimized to become the transformational plating technique used at Micro Plating today. 

Varying Phosphorous Concentrations of Electroless Nickel

Once again, electroless nickel plating services are defined as the auto-catalytic process used to leave metal deposits of a nickel-alloy coating on the part surface without introducing an electrical current frequently found in alternative electroplating procedures. Electroless plating deposits a uniform layer of alloy across the entire part surface that provides additional corrosion resistance, elevated hardness, improved durability, and added protection from galling. There are different phosphorus concentrations used in ENP and the exact concentration determines the end properties of the coating and can be broken down into three categories. Micro Plating does not currently offer low phosphorous electroless nickel, but both medium and high baths are RoHS compliant. 

• High Phosphorus ENP: The elevated phosphorous concentration in these baths is essential for RoHS and REACH-compliant projects that also conform to AMS 2404, AMS 2454, AMS-C-26074, ASTM B733, Mil-C-26074, and other specifications. This process is perfect for parts that will be exposed to harsh salt spray environments or other acidic conditions due to the excellent corrosion resistance provided by the coating. 

• Medium Phosphorus ENP: An excellent solution that blends the benefits between low and high phosphorus concentration baths. Medium phosphorus concentration electroless nickel plating services provide enhanced hardness, surface brightness, and an expedited plating rate. This process also meets the needs of REACH and RoHS-compliance as well as AMS-2404, AMS-C-26074, and ASTM B733.

• Low Phosphorus ENP: Ideal for applications that demand extremely robust RC hardness levels. Also performs well on products destined for corrosive alkaline environments with pH values greater than 7.0. Low phosphorous electroless nickel is not currently offered by Micro Plating.

Pre-Treatment Process for Premium ENP Results

As with any industrial coating process, producing a high-quality product requires a strict pretreatment inspection plan that is vital to the final results. The experienced professionals at Micro Plating take this incredibly seriously and take all precautions to deliver high-quality products. The pre-treatment process starts with a thorough inspection of the surface texture to remove any burrs, uneven surfaces, weld spatter, or sharp edges that can be frequently found in manufacturing or fabrication environments. These imperfections, however slight, can impact the overall effectiveness of electroless nickel plating services and produce an inferior product. 

Our team will also look for and remove any surface contaminants like grease or oil from the fabrication process as any unwanted solids will inhibit the nickel alloy from creating a solid bond with the part surface. While the parts will all undergo a series of pre-treatment baths and rinses, any visible residue will be wiped clean to improve the effectiveness of the wash and reduce additional contamination of the rinse baths. 

Step By Step: Electroless Nickel Plating Services

Once the parts destined for electroless nickel are inspected and cleaned, they can begin the process. Generally speaking, electroless nickel can be condensed into four individual steps, with each step being critical to the final quality. The specific bath composition is discussed in an additional section further below. 

• Pre-Treatment Baths & Rinses: All components or parts designated for electroless nickel plating services start by being submerged in a series of pretreatment baths and rinse tanks to properly clean and prepare the surface for treatment. Each bath contains a calculated concentration of chemicals that help remove any grease, oil, dirt, and other contaminants from the surface. After each chemical rinse, the parts are rinsed in clean water before being submerged in additional baths. This helps maintain the proper concentration in the cleaning baths and ensures each chemical agent works properly. 

• Activating the Surface Substrate: Once the parts are thoroughly rinsed, the metal substrate requires additional activation. Simply put, this activation process ensures that the surface molecules of the substrate are hydrophilic, or capable of interacting with the water molecules in the bath. Activation is predominately completed with the help of an acid to remove oxides. After the substrate surface has been activated, it is finally ready to begin the process of electroless nickel plating.

• Depositing Nickel Alloy: Now thoroughly cleaned and activated, the parts are fully immersed in the plating solution bath where a chemical reaction occurs that deposits nickel and phosphorus ions onto the surface of the metal substrate. At this point, the auto-catalytic reaction between the nickel and the reducing agent occurs without the need for anodes or an electrical current. Depending on the part and the specified thickness of the nickel coating, the electroless nickel process can be manipulated in varying increments with an average of 10 microns deposited per hour. 

• Final Inspection: Once the intended thickness of the nickel deposit is achieved, the parts are removed, rinsed, and dried. A post-treatment rinse is critical to remove any leftover chemicals that may produce stains on the surface once dried. At this point, all parts are inspected for possible defects or areas that did not receive proper coverage. Some customers may also require an anti-oxidation or anti-tarnish treatment of the parts including additional baking or heat treatment to further improve the hardness and adhesion of the coating.

Running A Bath: Creating An Ideal Environment for ENP

The different chemical concentrations and specific elements of the different baths have several important factors to consider. Each bath must be routinely maintained and optimized to guarantee a consistent plating rate through the production run, uniform deposits, and the final quality of the plating itself. 

• Ideal Bath Temperature: Bath temperature is the leading factor in determining the plating rate. Baths that maintain a lower temperature provide less available energy for the chemical reaction and thus produce a reduced plating rate. Alternatively, higher temperatures above the ideal conditions make the bath too chemically active and result in over-plating or general process instability that may lead to wasted material or expensive re-work. To maintain optimal temperatures, Micro Plating utilizes automatic temperature controllers to frequently calibrate the bath temperatures and to provide optimal plating results. 

• Metal Source: For electroless plating the metal source used is in the form of a soluble nickel salt like nickel sulfate. However, other processes incorporate nickel chloride, nickel sulfamate, nickel acetate, and nickel hypophosphate into the bath. Prices and results may vary depending on the specific metal source used. 

• Reducing Agent: A reducing agent is a substance that loses electrons to other substances through a redox reaction and replaces the rectifier typically found in traditional electroplating applications. Common reducing agents used in plating baths are sodium borohydride, sodium hypophosphite, and dimethylamine borine. Most electroless nickel platers will keep the actual composition of the chemical baths proprietary and will not readily disclose this agent to their customers or the public. 

• Adding Complexants: Complexants, or complexing agents, keep the available nickel ions in a stable condition until they are required for plating. The added complexant may change depending on the specific deposit alloy and the final coating properties desired by the customer. Some complexants used in electroless nickel baths are carboxylic acids that increase the solubility of phosphorus.

• Varying Buffers: Plating baths will generate excess hydrogen gas as well as ionic hydrogen that will alter the pH of the ENP bath towards the acidic side of the scale. This excess acidity must be neutralized with buffers to maintain the correct plating conditions. For many platers, the most common buffer used is ammonium hydroxide. However, due to the smell and the many complications for proper disposal, many electroless nickel providers, including Micro Plating, are switching to alternative buffers like sodium hydroxide to adjust the bath pH levels and maintain optimal performance. 

• Stabilizing Agents: Stabilizers are used in the electroless nickel plating bath to control the plating reaction. Without stabilizers, the reaction can become unstable and lead to undesirable results. The two main categories of stabilizers are organic and metallic. Stabilizer levels that fall beneath the optimal concentration will impact the deposition rate and the overall bath stability. When these levels are elevated, the plating reaction may be inhibited and even come to a complete stop.

• Enhancing Brightness: For certain applications of electroless nickel plating, customers will expect a specific aesthetic appearance or surface finish. In this case, brighteners can be added to enhance the deposit's final appearance. The surface finish of can be matte to semi-bright or even extremely bright to meet certain decorative or aesthetic requirements. 

How Does ENP Differ from Anodizing?

There is one stark difference between electroless nickel plating and anodizing. Anodizing does not produce quality plating results with only chemicals and requires added electrical current to facilitate the necessary reaction. Through the electrochemical process of anodizing, metal parts are coated with a surface layer of oxide that provides additional sturdiness and a visually pleasing appearance. Anodizing is frequently used for aluminum, but can also utilize other substrates like magnesium and titanium. Anodizing is limited for certain applications as it struggles to provide an adequate surface coating on steel components. 

How Does ENP Differ from Hard Chrome?

Electroless nickel plating and hard chrome finishings both work on a variety of substrate materials and produce a uniform and protective finish layer. Both coatings are incredibly durable and offer considerable longevity in environments prone to corrosion and wear, even with constant mechanical contact. However, some crucial differences exist that make electroless nickel a preferred option over hard chrome. Electroless nickel provides superior corrosion protection versus hard chrome especially when exposed to harsh salt spray conditions.  Additionally, ENP is also capable of reaching and uniformly coating the deep recesses of intricate designs. Hard chrome plating also requires an electrical current, making it the more expensive of the two finishing options. 

The Numerous Benefits of Electroless Nickel Plating Services

Electroless plating is an incredibly versatile and beneficial plating option for a wide range of industries. Many of these benefits are listed below:

• Resistance to Corrosion: Electroless nickel results in less porous surface coating than other alternative plating methods. The extremely hard-finished surface offers exceptional corrosion resistance to common environmental elements such as salt spray, oxygen, carbon dioxide, and even more corrosive agents like hydrogen sulfide. 

• Conductivity: This process can provide a conductive surface to a non-conductive substrate like plastic. This has proven incredibly useful in the manufacturing of electronic equipment and provides conductive properties to connector pins, circuit boards, or transistor chips. 

• Robust Hardness: As discussed above, the phosphorus bath concentration determines the final hardness level. The overall hardness grade is measured using the Rockwell Hardness Scale, which provides a hardness value based on the indentation of a material. High phosphorus concentrations (10-14%) provide the lowest level of hardness while medium phosphorus concentrations (5-9%) offer balanced hardness levels and corrosion resistance to the final coating.

• Uniform Coating: All parts receive an even and uniform protective coating without running the risk of over or under-plated areas. This process is capable of penetrating deep bores and recesses while evenly coating corners and edges without depositing excess coating. ENP can hold thickness tolerances within 0.0002” or smaller, if necessary. 

• Added Characteristics & Appearance: Electroless nickel services provide several advantages relevant to the additional fabrication or end applications. This process has the potential to improve ductility (the ability of a metal to stretch rather than break), lubricity (overall receptiveness of lubrication), and enhanced electrical properties for specific applications. Electroless nickel plating is also non-magnetic. Finally, through the manipulation of concentrations of certain chemicals in the baths, the finish appearance can be matte, semi-bright, or bright. 

• Comprehensive Cost Savings: By definition, electroless plating does not require electricity to produce the final coating, and those subsequent cost-savings are passed on to the end customer. Additionally, cost-savings extend beyond the initial production phase with these parts lasting longer in their end application, providing better performance, and requiring less maintenance. 

Common Applications For Electroless Nickel Plating Services

Micro Plating has spent years working with customers in countless industries to produce premium quality parts with electroless nickel that are competitively priced and outperform competing solutions. Some examples of common applications for our nickel plating services include:

• Automotive Components: Frequently plate the various gears, cylinders, brake pistons, heat sinks, shock absorbers, and other metal components that will be exposed to mechanical wear and corrosive elements.

• Aerospace, Defense, & Military: Micro Plating can provide coatings that meet or exceed Mil-C-26074, MILDTL-32199, AMS 2404, AMS 2454, and additional specifications required for aerospace, defense, and other military applications. 

• Electrical Devices: The uniform application, corrosion resistance, and enhanced solderability of electroless nickel-plated parts make them ideal for electrical components like hard drives, circuit boards, semiconductors, and other connectors used in complex electrical devices.

• Oil & Gas Industry: The production and transportation of oil or gas are highly dependent on valves, pipe fittings, and pumps that receive electroless nickel plating services to help withstand corrosive chemicals, high pressures, consistent use, and exposure to environmental conditions.

• Textile Manufacturing: Textile production uses considerable moving parts that necessitate the enhanced levels of wear resistance and durability provided by electroless nickel plating. 

• Rubber Molding: Our electroless nickel plating services can be used on mold plates to provide a durable coating that can withstand repeated use and high temperatures, and hold the tight tolerances demanded by our customers. 

• Pharmaceutical: For example, dies used in the pharmaceutical industry require a durable finish as well as tight tolerances. With intricately designed parts and components, the pharmaceutical industry is quickly recognizing and applying the benefits of electroless plating. 

Working With Micro Plating Inc.

Micro Plating Inc. is an industry leader and has completed countless electroless nickel plating jobs for clients in the CNC machining, military, injection molding, automotive, and aerospace industries all to varying thickness levels from as thin as 0.00005” to 0.003”. Micro Plating can match all necessary specifications for challenging industries including MIL-C-26074, AMS-C-26074, and ASTM B 733. With decades of combined experience manning our facility, Micro Plating is confident that we can produce a highly uniform and precise end product that reduces costs, expedites turnaround times, and improves part resistance to corrosion, temperatures, and abrasion. Please contact a member of our team at any time if you have a project requiring electroless nickel plating services or simply want to learn more about our company and capabilities. 

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